Photochromic polystyrene film as well as preparation method and application thereof

Abstract

The invention discloses a photochromic polystyrene film and a preparation method and application thereof, the photochromic polystyrene film is an electrostatic spinning fiber film of modified polystyrene, the structural formula of the modified polystyrene is as follows: # imgabs0 #, m is an integer between 100 and 800, and n is an integer between 20 and 200. The photochromic polystyrene film has UV photoresponse performance, the color of the film is mustard gold, the color of the film is changed from mustard gold to yellowish brown under ultraviolet irradiation, when the film is yellowish brown, the film is changed from yellowish brown to mustard gold after visible light irradiation, and the change has reversibility, can be converted for multiple times and can be used for anti-counterfeiting and information encryption.

Description

Technical Field

[0001] The present application relates to the field of anti-counterfeiting and information encryption, and in particular to a photochromic polystyrene film and a preparation method and application thereof. Background Art

[0002] Expanded polystyrene has the characteristics of light weight, moisture resistance, heat insulation, shock absorption, impact resistance, and easy processing and molding. It is widely used in construction, packaging, electronic products, automobile manufacturing and other fields. The amount of expanded polystyrene waste is large, and due to its stable chemical properties, it is difficult to degrade in nature, which brings great harm to the environment. The commonly used incineration and landfill treatment methods not only pollute the environment, but also cause serious waste of resources.

[0003] Stimuli-responsive films can react to environmental triggers (such as light, heat, mechanical force, etc.) by changing visual color or shape. The research and development of advanced smart materials based on stimuli-responsive films has attracted widespread attention. Light stimuli-responsive films have the advantages of non-contact, remote control, and fast response speed. These excellent properties make them have important potential applications in the fields of sensing, optical devices, security and anti-counterfeiting, data storage, and intelligent robots. However, most of the existing light stimuli-responsive films have problems such as cumbersome preparation process, complex process, and unstable performance.

[0004] Polystyrene materials have good solubility and spinnability, and fiber membranes can be made from them using electrospinning technology. Electrospinning technology has the advantages of simple operation, energy saving, and functionalization, and is considered to be a more mature and effective functional polymer membrane preparation technology. At the same time, the benzene ring structure of polystyrene has good nucleophilic ability. Different active groups can be introduced on the benzene ring through common unit reactions such as alkylation, sulfonation, and nitration, which can provide active reaction sites for the introduction of photoresponsive functional groups. Therefore, by combining common chemical reactions and simple electrospinning technology, waste foamed polystyrene can be used to design and develop light-responsive smart membrane materials with important application value. On the other hand, polystyrene membrane materials have hydrophobic / oleophilic surface wettability, and this special surface wettability makes it have application potential in the field of oil-water separation. The treatment of industrial oily wastewater is also one of the important environmental problems. Therefore, light-responsive membrane materials based on waste foamed polystyrene are also expected to be used for the treatment of oily wastewater and realize the multifunctional reuse of plastic waste. Summary of the invention

[0005] The excellent reactivity of the benzene ring structure in the polystyrene molecule allows it to introduce different active groups (such as sulfonic acid, nitro, chloromethyl, etc.) on the benzene ring through common unit reactions, which can provide active reaction sites for the introduction of photoresponsive groups. At the same time, the polystyrene material itself has good solubility and spinnability, and can be made into functional fiber membranes using electrospinning technology. The azobenzene group has ultraviolet (UV) light response characteristics, that is, it can show trans and cis isomerization under ultraviolet and visible light, resulting in a change in the color of the azobenzene material.

[0006] This application combines the UV light response characteristics of azobenzene with the excellent reactivity and film-forming properties of polystyrene, and uses chemical modification and electrospinning technology to design and develop a photochromic polystyrene-based functional film that can be used for anti-counterfeiting or information encryption, thereby achieving the purpose of high-value utilization of waste foamed polystyrene.

[0007] Based on this, the present invention provides a photochromic polystyrene film with a simple preparation process and a preparation method and application thereof, which can solve the problems of cumbersome process, complex process and unstable performance of the existing photochromic film preparation technology.

[0008] Application of photochromic polystyrene film in anti-counterfeiting or information encryption, wherein the photochromic polystyrene film is an electrostatic spinning fiber film of modified polystyrene, wherein the structural formula of the modified polystyrene is as follows:

[0009]

[0010] Herein, m is an integer between 100 and 800, and n is an integer between 20 and 200.

[0011] The present application also provides a photochromic polystyrene film, wherein the photochromic polystyrene film is an electrospun fiber film of modified polystyrene, wherein the structural formula of the modified polystyrene is as follows:

[0012]

[0013] Herein, m is an integer between 100 and 800, and n is an integer between 20 and 800.

[0014] For example, the number average molecular weight of the modified polystyrene polymer ranges from 30,000 to 100,000.

[0015] The photochromic polystyrene film has UV light response performance, and the color of the film is mustard gold. When the film is irradiated with UV light, the color of the film changes from mustard gold to yellowish brown. When the film is yellowish brown, after being irradiated with visible light, the film changes from yellowish brown to mustard gold, and this transformation is reversible and can be converted multiple times. Therefore, it can be used for anti-counterfeiting and information encryption.

[0016] Optionally, the fiber diameter of the electrospun fiber membrane of modified polystyrene is 1.0 to 12.0 μm.

[0017] The present application also provides a method for preparing the photochromic polystyrene film, comprising:

[0018] (1) treating polystyrene with a chloromethylation agent to obtain chloromethylated polystyrene;

[0019] (2) adding a modifying agent to the chloromethylated polystyrene obtained in step (1) to introduce an azobenzene structure into the polystyrene structure to obtain a modified polystyrene; the modifying agent is 4-hydroxyazophenol;

[0020] (3) dissolving the modified polystyrene obtained in step (2) in a first organic solvent to prepare a spinning solution, and preparing a photochromic polystyrene film by electrospinning.

[0021] In step (1):

[0022] Optionally, the reaction process between the chloromethylation agent and polystyrene includes:

[0023] The polystyrene is dissolved in a second organic solvent, a first catalyst is added, and then a chloromethylation agent is added to react to obtain a first reaction liquid, and the chloromethylated polystyrene is separated from the first reaction liquid.

[0024] Optionally, the second organic solvent is dichloromethane, chloroform or carbon tetrachloride.

[0025] Optionally, the first catalyst is anhydrous tin tetrachloride.

[0026] Optionally, the chloromethylation agent is 1,4-dichloromethoxybutane and the molar ratio of the chloromethylation agent to the polystyrene is 1.5:1 to 10:1.

[0027] Optionally, the reaction temperature is room temperature and the reaction time is 12 to 24 hours.

[0028] Optionally, the polystyrene is waste polystyrene foam.

[0029] Optionally, the mass ratio of the first catalyst to polystyrene is 3:1 to 1:1.

[0030] In step (2):

[0031] Optionally, the reaction process between the modifying agent and the chloromethylated polystyrene includes:

[0032] The modifying agent and the chloromethylated polystyrene are respectively dissolved in the first organic solvent, a second catalyst is added to react to obtain a second reaction liquid, and the modified polystyrene is separated from the second reaction liquid.

[0033] Optionally, the molar ratio of the modifying agent to the chloromethylated polystyrene is 1:1 to 4:1.

[0034] Optionally, the second catalyst is potassium carbonate and potassium iodide.

[0035] Optionally, the molar ratio of the potassium carbonate to the chloromethylated polystyrene is 1:1 to 3:1.

[0036] Optionally, the potassium iodide accounts for 5-20 wt% of the potassium carbonate; preferably, the potassium iodide accounts for 7-12 wt% of the potassium carbonate.

[0037] Optionally, the reaction conditions are: reaction temperature is 50-90°C, and reaction time is 5-10 hours. Preferably, the reaction conditions are: reaction temperature is 60-80°C, and reaction time is 6-8 hours.

[0038] Optionally, the first organic solvent used in this step is the same as the first organic solvent in step (3).

[0039] In step (3):

[0040] Optionally, the first organic solvent is N,N-dimethylformamide or N,N-dimethylacetamide.

[0041] Optionally, the spinning solution concentration is 10-60 wt %. Preferably, the spinning solution concentration is 20-40 wt %.

[0042] Optionally, the electrospinning conditions are: positive voltage of 10-15 kV, negative voltage of 2-6 kV, syringe advancement speed of 0.1-0.8 mm / min, receiving distance of 15-40 cm, and receiver speed of 3000-6000 r / h. Preferably, the electrospinning conditions are: positive voltage of 12-14 kV, negative voltage of 2-4 kV, syringe advancement speed of 0.2-0.4 mm / min, receiving distance of 20-30 cm, and receiver speed of 4200-5400 r / h.

[0043] Optionally, separating the chloromethylated polystyrene from the first reaction liquid and separating the modified polystyrene from the second reaction liquid respectively include: adding the first reaction liquid or the second reaction liquid to ethanol or water for precipitation to obtain a precipitate, and vacuum drying the precipitate.

[0044] Optionally, the process conditions for vacuum drying the precipitate are: temperature 50-100° C., time 8-12 h. Preferably, the process conditions for vacuum drying are: temperature 60-70° C., time 10-12 h.

[0045] Compared with the prior art, the photochromic polystyrene film and its preparation method and application in the present application have at least one of the following technical effects:

[0046] (1) The present invention uses waste polystyrene foam as raw material, uses chemical reaction to bond 4-hydroxyazophenol containing UV responsive groups (azobenzene) to polystyrene macromolecular chains, and finally prepares a photochromic polystyrene film by electrostatic spinning technology. Among them, for the prepared photochromic polystyrene film, the surface color of the film can be changed from mustard gold to yellow brown by UV stimulation, and this transformation is reversible, flexible, and has stable performance.

[0047] (2) The membrane can be used for intelligent anti-counterfeiting or information encryption, and can also be used for the efficient separation of oily wastewater in a variety of different systems (such as oil-water mixtures and oil-in-water emulsions), and the membrane has good recycling performance.

[0048] (3) The photochromic polystyrene film preparation process of the present application is simple, the raw material cost is low, the applicability is wide, and it is multi-purpose, and is suitable for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the modified polystyrene prepared in Example 1 of the present invention.

[0050] Figure 2 This is a photo of the photochromic polystyrene film sample prepared in Example 2 of the present invention.

[0051] Figure 3 This is a scanning electron microscope photograph of the photochromic polystyrene film prepared in Example 2 of the present invention.

[0052] Figure 4 This is a photo of the polystyrene fiber membrane sample prepared in Comparative Example 1 of the present invention.

[0053] Figure 5 The UV-visible absorption spectra of the N-methyl-2-pyrrolidone solution of the modified polystyrene prepared in Example 2 of the present invention under UV light (a) and visible light (b) irradiation time at different times.

[0054] Figure 6 The trans-cis (a) and cis-trans (b) isomerization kinetic curves of the modified polystyrene prepared in Example 2 of the present invention in N-methyl-2-pyrrolidone solution.

[0055] Figure 7This is a graph showing the reversible changes in the absorption peak intensity at 350nm and 440nm of the N-methyl-2-pyrrolidone solution of the photochromic polystyrene prepared in Example 2 of the present invention under alternating irradiation of ultraviolet light and visible light.

[0056] Figure 8 The color change of the photochromic polystyrene film prepared in Example 2 of the present invention under alternating irradiation of ultraviolet light and visible light.

[0057] Fig. 9 This is the color change of the polystyrene fiber membrane prepared in Comparative Example 1 of the present invention under alternating irradiation of ultraviolet light and visible light.

[0058] Fig.10 Schematic diagram of the process of making an anti-counterfeit label using the photochromic polystyrene film prepared in Example 2 of the present invention (a) and the anti-counterfeit label (b).

[0059] Fig.11 The ASCII binary code is made using the photochromic polystyrene film prepared in Example 2 of the present invention.

[0060] Fig.12 A two-dimensional code is made using the photochromic polystyrene film prepared in Example 2 of the present invention.

[0061] Fig.13 The contact angle test results of water (a) and oil (b) in air for the photochromic polystyrene film prepared in Example 2 of the present invention.

[0062] Fig.14 The test results of the contact angles of water (a) and oil (b) in air for the polystyrene fiber membrane prepared in Comparative Example 1 of the present invention.

[0063] Fig.15 The process and results of the separation experiment of the oil-water mixture (a) and the water-in-oil emulsion (b) of the photochromic polystyrene film prepared in Example 2 of the present invention.

[0064] Fig.16 This is a flow chart of the method for preparing the photochromic polystyrene film of the present application. DETAILED DESCRIPTION

[0065] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0067] Fig.16 The figure is a flow chart of the method for preparing a photochromic polystyrene film; the corresponding steps are described in detail below in conjunction with various embodiments.

[0068] The chemical reagents used in the following examples are all commercially available.

[0069] Example 1

[0070] Preparation of modified polystyrene:

[0071] 0.500 g of waste polystyrene foam plastic fragments were dissolved in 15.00 mL of carbon tetrachloride, 0.375 mL of anhydrous tin tetrachloride was added, and then 1.50 mL of 1,4-dichloromethoxybutane was dropped. The mixture was stirred at room temperature for 16 h, and then precipitated in ethanol, filtered, washed, and vacuum dried at 60 ° C for 12 h to obtain chloromethylated polystyrene.

[0072] After dissolving 0.200 g of chloromethylated polystyrene in 8.00 mL of N,N-dimethylformamide, 0.400 g of 4-hydroxyazophenol, 0.400 g of anhydrous potassium carbonate and 0.040 g of potassium iodide were added, the temperature was raised to 70°C, stirred for 7 hours, then precipitated in water, filtered, washed with acetonitrile, and vacuum dried at 60°C for 12 hours to obtain modified polystyrene.

[0073] Figure 1 The hydrogen nuclear magnetic resonance spectrum of the modified polystyrene obtained in Example 1. The peaks at 7.03ppm and 6.57ppm are attributed to the chemical shift of hydrogen protons on the benzene ring of polystyrene, the peaks at 1.81ppm and 1.40ppm are attributed to the chemical shift of hydrogen protons in the polystyrene skeleton structure, the peak at 4.94ppm is attributed to the chemical shift of hydrogen protons in the methyleneoxy group, and the peaks at 7.47 and 7.89ppm are attributed to the chemical shift of hydrogen protons on the benzene ring of azobenzene. The above results confirm that the azobenzene UV response group is successfully introduced into the molecular structure of polystyrene, and modified polystyrene is obtained from waste polystyrene foam.

[0074] Example 2

[0075] Preparation of photochromic polystyrene film:

[0076] 1.000 g of the modified polystyrene prepared in Example 1 was dissolved in 3.70 mL of N,N-dimethylformamide and stirred to form a spinning solution. The spinning solution was injected into a spinneret and spun using an electrostatic spinning machine to obtain a photochromic polystyrene film. The positive voltage was 13 kV, the negative voltage was 2 kV, the syringe advancement speed was 0.3 mm / min, the receiving distance was 20 cm, and the receiver speed was 4800 r / h.

[0077] Figure 2 This is a photo of the photochromic polystyrene film sample prepared in Example 2. The film has a mustard gold appearance, and the fibers on the surface of the film are uniform and dense. Figure 3 This is a scanning electron microscope photograph of the photochromic polystyrene film prepared in Example 2. It can be seen that the fibers in the film are uniform in thickness and have a smooth surface, and the fibers are interlaced to form a network structure.

[0078] Comparative Example 1

[0079] Preparation of polystyrene fiber membrane:

[0080] 2.000 g of discarded polystyrene foam plastic fragments were weighed and dissolved in 40.00 mL of dichloromethane, precipitated in ethanol, filtered, and vacuum dried at 60° C. for 12 h to obtain recovered polystyrene.

[0081] Compared with Example 2, only the modified polystyrene in Example 2 was replaced with recycled polystyrene to prepare a polystyrene fiber membrane.

[0082] Figure 4 This is a photo of a polystyrene fiber film sample prepared in Comparative Example 1. The film is white in appearance, which is obviously different from the photoluminescent polystyrene film prepared in Example 2.

[0083] Application Example 1

[0084] UV light responsiveness of photochromic polystyrene films:

[0085] Figure 5 Part (a) is the UV-visible absorption spectra of the N-methyl-2-pyrrolidone solution of the modified polystyrene prepared in Example 1 after 365nm UV irradiation for different times. It can be seen that the absorption band of the solution at 350nm (attributed to the π-π* transition of the azobenzene structure) gradually weakens with the increase of UV irradiation time, while the absorption band at 440nm (attributed to the n-π* transition) gradually strengthens with the increase of UV irradiation time, and is in a photostable state after 30s of UV irradiation. This is because the azobenzene structure in the modified polystyrene gradually changes from the trans configuration to the cis configuration under UV irradiation. Figure 5Part (b) is the UV-visible absorption spectrum of the above solution after continued exposure to visible light for different time periods. It can be seen that with the increase in visible light exposure time, the absorption band of the solution at 350nm gradually increases, while the absorption band at 440nm gradually weakens. After 20 minutes of visible light exposure, the absorption peak intensity basically returns to the state before UV exposure. This is because the azo structure gradually changes from the cis configuration to the trans configuration under visible light.

[0086] Figure 6 Part (a) and part (b) are the trans-cis and cis-trans isomerization kinetic curves of the N-methyl-2-pyrrolidone solution of the modified polystyrene prepared in Example 1. It can be seen that the isomerization of the modified polystyrene conforms to the first-order kinetic reaction. The figure shows that the trans-cis and cis-trans isomerization reaction rate constants of the modified polystyrene are 0.20017s -1 and 0.12655s -1 , confirming that the modified polystyrene prepared in Example 1 has a rapid UV stimulus response characteristic, and this rapid response is reversible ( Figure 7 ).

[0087] Figure 8 The following are photos of the photochromic polystyrene film prepared in Example 2 before and after 365nm UV irradiation. The film appears mustard gold before UV irradiation, and changes to yellow-brown after UV irradiation. The CIE color coordinates of the film before and after UV irradiation are L * 、a * 、b * They are 52.59, 13.34, 73.82 and 41.26, 24.71, 70.05 respectively. According to the formula The calculated color difference value ΔE is 16.49. The above results confirm that the photochromic polystyrene film prepared in Example 2 has reversible light response performance, that is, the color of the film can be changed from mustard gold to yellow brown after UV irradiation, and the color of the film is changed from yellow brown to mustard gold again when the film is continuously irradiated with visible light. This is because the azobenzene structure in the modified polystyrene is changed from trans configuration to cis configuration under UV irradiation, and from cis configuration to trans configuration under visible light irradiation. Utilizing this reversible cis-trans isomerization process, by changing the light source (UV light and visible light), the color of the film surface can be switched between mustard gold and yellow brown multiple times, and because the color difference between the two colors is relatively obvious (ΔE>12), this color change is easy to distinguish with the naked eye, which is suitable for anti-counterfeiting applications.

[0088] Attached Fig. 9 The polystyrene fiber membrane prepared in Comparative Example 1 was subjected to UV light and visible light irradiation. It was found that the color of the membrane surface did not change significantly after changing the light source.

[0089] The above results indicate that, unlike the photochromic polystyrene film prepared from modified polystyrene, the fiber membrane prepared from recycled polystyrene without the introduction of azobenzene structure has no UV responsiveness, which confirms that the azobenzene structure in the modified polystyrene is the key to the reversible photoresponsive color change of the photochromic polystyrene film.

[0090] Application Example 2

[0091] Brand anti-counterfeiting:

[0092] Fig.10 Part (a) is a schematic diagram of the process of making an anti-counterfeiting label using the photochromic polystyrene film prepared in Example 2, and part (b) is the prepared anti-counterfeiting label. It can be seen that under the irradiation of 365nm UV light, the brand pattern on the anti-counterfeiting label gradually appears, and the brand pattern gradually disappears when the visible light irradiation is continued. The change is discernible to the naked eye, and the process can be repeated many times. Therefore, brand anti-counterfeiting can be achieved by switching the light source. This proves that the photochromic polystyrene film prepared by the present invention can be used in the field of anti-counterfeiting.

[0093] Application Example 3

[0094] Information encryption and information transmission:

[0095] Fig.11 and Fig.12 The application of the photochromic polystyrene film prepared in Example 2 in information encryption and information transmission. Fig.10 In the production process of part (a), the brand pattern hollow template is replaced with an ASCII binary code hollow template and a QR code hollow template, and binary codes with information encryption and transmission functions are made of photochromic polystyrene film ( Fig.11 ) and QR code ( Fig.12 ).like Fig.11 As shown, the binary code can be revealed under 365nm UV light and can be converted into the English word "OK" to achieve information transmission, while the binary code gradually disappears under visible light. Fig.12 The QR code prepared in the invention is an upgraded encryption model. The QR code can be displayed under 365nm UV light and can be scanned by a smart phone to access the "Jiaxing University" webpage. However, under visible light, the QR code gradually disappears. The above results confirm that the photochromic polystyrene film prepared by the present invention can be used to design a variety of complex information encryption modes, which can be applied to the fields of advanced information encryption and information transmission.

[0096] Application Example 4

[0097] Surface wettability of photochromic polystyrene film:

[0098] Fig.13The contact angle test results of the photochromic polystyrene film prepared in Example 2. It can be seen that the contact angle of water in the air is 123.3°, and the contact angle of oil is 0°, which indicates that the prepared membrane has good hydrophobicity / lipophilicity and can be used for oil-water separation.

[0099] Fig.14 The contact angle test results of the polystyrene fiber membrane prepared in Comparative Example 1 are shown. It can be seen that the contact angle of water in the air is 117.6°, and the contact angle of oil is 0°, and the membrane exhibits good hydrophobicity / lipophilicity.

[0100] The above results show that the photochromic polystyrene film prepared from modified polystyrene in Example 2 and the polystyrene fiber film prepared from recycled polystyrene in Comparative Example 1 both exhibit hydrophobicity / lipophilicity, confirming that the surface wettability of the film is mainly based on the properties of polystyrene itself, and the introduction of azobenzene structure does not affect the wettability of the film surface. Therefore, the prepared photochromic polystyrene film exhibits dual functionality, namely, light response and hydrophobicity / lipophilicity. Therefore, the photochromic polystyrene film prepared by the present invention can be used not only in the fields of anti-counterfeiting and information encryption, but also in the field of oil-water separation.

[0101] Application Example 5

[0102] Separation of oil-water mixture:

[0103] 30.00 mL of oil (n-hexane) and 30.00 mL of deionized water dyed with methylene blue were mixed to prepare an oil-water mixture. The photochromic polystyrene membrane prepared in Example 2 was used to separate the oil-water mixture prepared above. The separation process and results are shown in FIG. Fig.15 As shown in part (a) of the diagram, it can be seen that the oil passes through the membrane and the water is retained because the membrane has hydrophobic / lipophilic properties. According to the experimental results, the oil separation flux is calculated to be as high as 6790.88 L·m -2 ·h -1 The separation efficiency is as high as 99.82%, and the separation flux is still 6520.00 L·m after 10 cycles. -2 ·h -1 The above results show that the separation efficiency is still above 99.60%. The above results prove that the photochromic polystyrene membrane prepared by the present invention can efficiently separate oil-water mixture and has excellent recyclability.

[0104] Application Example 6

[0105] Separation of water-in-oil emulsions:

[0106] 2 mg of Span 80 was added to 49.00 mL of oil (n-hexane), and then 1.00 mL of deionized water was added to the above solution, and the mixture was stirred thoroughly to obtain an oil-in-water emulsion. The above-prepared oil-in-water emulsion was separated using the photochromic polystyrene membrane prepared in Example 2. The separation process and results are shown in FIG. Fig.15 As shown in part (b) of the experiment, it can be seen that the water-in-oil emulsion before separation is an opaque emulsion, and after separation it is a clear and transparent oil. According to the experimental results, the oil separation flux is calculated to be as high as 7073.55 L·m -2 ·h -1 The separation efficiency reached 99.60%, and the separation flux was still 6520.00 L·m after 10 cycles. -2 ·h -1 The separation efficiency is still above 99.00%, which proves that the photochromic polystyrene membrane prepared by the present invention can efficiently separate water-in-oil emulsions and has excellent recycling performance.

[0107] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. Application of photochromic polystyrene film in anti-counterfeiting or information encryption, characterized in that: The photochromic polystyrene film is an electrostatically spun fiber film of modified polystyrene, wherein the structural formula of the modified polystyrene is as follows: Herein, m is an integer between 100 and 800, and n is an integer between 20 and 200.

2. The use according to claim 1, characterized in that: The fiber diameter of the modified polystyrene electrospun fiber membrane is 1.0-12.0 μm.

3. A photochromic polystyrene film, characterized in that: The photochromic polystyrene film is an electrostatically spun fiber film of modified polystyrene, wherein the structural formula of the modified polystyrene is as follows: Herein, m is an integer between 100 and 800, and n is an integer between 20 and 200.

4. The photochromic polystyrene film according to claim 3, characterized in that: The fiber diameter of the modified polystyrene electrospun fiber membrane is 1.0-12.0 μm.

5. The method for preparing a photochromic polystyrene film according to claim 3 or 4, characterized in that: include: (1) treating polystyrene with a chloromethylation agent to obtain chloromethylated polystyrene; (2) adding a modifying agent to the chloromethylated polystyrene obtained in step (1) to introduce an azobenzene structure into the polystyrene structure to obtain a modified polystyrene; the modifying agent is 4-hydroxyazophenol; (3) dissolving the modified polystyrene obtained in step (2) in a first organic solvent to prepare a spinning solution, and preparing a photochromic polystyrene film by electrospinning.

6. The preparation method according to claim 5, characterized in that: In step (1), the reaction process between the chloromethylation agent and polystyrene includes: The polystyrene is dissolved in a second organic solvent, a first catalyst is added, and then a chloromethylation agent is added to react to obtain a first reaction liquid, and the chloromethylated polystyrene is separated from the first reaction liquid.

7. The preparation method according to claim 6, characterized in that: The second organic solvent is dichloromethane, chloroform or carbon tetrachloride; The first catalyst is anhydrous tin tetrachloride; The chloromethylation agent is 1,4-dichloromethoxybutane, and the molar ratio of the chloromethylation agent to the polystyrene is 1.5:1 to 10:

1.

8. The preparation method according to claim 5, characterized in that: In step (2), the reaction process between the modifying agent and the chloromethylated polystyrene includes: The modifying agent and the chloromethylated polystyrene are respectively dissolved in the first organic solvent, a second catalyst is added to react to obtain a second reaction liquid, and the modified polystyrene is separated from the second reaction liquid.

9. The preparation method according to claim 8, characterized in that: The molar ratio of the modifying agent to the chloromethylated polystyrene is 1:1 to 4:1; The second catalyst is potassium carbonate and potassium iodide.

10. The preparation method according to claim 5, characterized in that: In step (3), the first organic solvent is N,N-dimethylformamide or N,N-dimethylacetamide; The concentration of the spinning solution is 10 to 60 wt%; The electrospinning conditions are: The positive voltage is 10-15 kV, the negative voltage is 2-6 kV, the syringe advancement speed is 0.1-0.8 mm / min, the receiving distance is 15-40 cm, and the receiver rotation speed is 3000-6000 r / h.

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